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A287650 Number of doubly symmetric diagonal Latin squares of order 2n with constant first row. 4
0, 2, 0, 12288 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A doubly symmetric square has symmetries in both the horizontal and vertical planes.

One plane symmetry requires one-to-one correspondence between values of elements a[i][j] and a[N-i][j] in vertical plane and between values of elements a[i][j] and a[i][N-j] in horizontal plane for all i and j values (numbering if indexes from 1). - Eduard I. Vatutin, Alexey D. Belyshev, Oct 09 2017

It seems that doubly symmetric diagonal Latin squares exists only for orders N == 0 (mod 4). - Eduard I. Vatutin, Oct 18 2017

LINKS

Table of n, a(n) for n=1..4.

E. I. Vatutin, Discussion about properties of diagonal Latin squares at forum.boinc.ru, value a(4) is wrong (in Russian)

E. I. Vatutin, Discussion about properties of diagonal Latin squares at forum.boinc.ru, corrected value a(4) (in Russian)

E. I. Vatutin, S. E. Kochemazov, O. S. Zaikin, Estimating of combinatorial characteristics for diagonal Latin squares, Recognition — 2017 (2017), pp. 98-100 (in Russian)

E. I. Vatutin, S. E. Kochemazov, O. S. Zaikin, On Some Features of Symmetric Diagonal Latin Squares, CEUR WS, vol. 1940 (2017), pp. 74-79.

E. I. Vatutin, S. E. Kochemazov, O. S. Zaikin, V. S. Titov, Investigation of the properties of symmetric diagonal Latin squares, Proceedings of the 10th multiconference on control problems (2017), vol. 3, pp. 17-19 (in Russian)

E. I. Vatutin, S. E. Kochemazov, O. S. Zaikin, V. S. Titov, Investigation of the properties of symmetric diagonal Latin squares. Working on errors, Intellectual and Information Systems (2017), pp. 30-36 (in Russian)

Index entries for sequences related to Latin squares and rectangles

FORMULA

a(n) = A292517(n)/n!.

EXAMPLE

Doubly symmetric diagonal Latin square example:

0 1 2 3 4 5 6 7

3 2 7 6 1 0 5 4

2 3 1 0 7 6 4 5

6 7 5 4 3 2 0 1

7 6 3 2 5 4 1 0

4 5 0 1 6 7 2 3

5 4 6 7 0 1 3 2

1 0 4 5 2 3 7 6

Reversion of all rows is equivalent to the exchange of elements 0 and 7, 1 and 6, 2 and 5, 3 and 4; hence, this square is horizontally symmetric. Reversion of all columns is equivalent to the exchange of elements 0 and 1, 2 and 4, 3 and 5, 6 and 7; hence, the square is also vertically symmetric.

CROSSREFS

Cf. A003191, A287649, A292517.

Sequence in context: A265594 A269904 A090446 * A270830 A270829 A104157

Adjacent sequences:  A287647 A287648 A287649 * A287651 A287652 A287653

KEYWORD

nonn,more,bref,changed

AUTHOR

Eduard I. Vatutin, May 29 2017

EXTENSIONS

a(4) corrected by Eduard I. Vatutin, Alexey D. Belyshev, Oct 09 2017

STATUS

approved

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Last modified December 16 20:54 EST 2017. Contains 296092 sequences.